mirror of https://github.com/hsoft/collapseos.git
108 lines
2.0 KiB
NASM
108 lines
2.0 KiB
NASM
; Sets Z is A is ' ' or '\t' (whitespace)
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isWS:
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cp ' '
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ret z
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cp 0x09
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ret
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; Advance HL to next WS.
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; Set Z if WS found, unset if end-of-string.
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toWS:
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ld a, (hl)
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call isWS
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ret z
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cp 0x01 ; if a is null, carries and unsets z
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ret c
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inc hl
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jr toWS
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; Consume following whitespaces in HL until a non-WS is hit.
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; Set Z if non-WS found, unset if end-of-string.
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rdWS:
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ld a, (hl)
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call isWS
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jr nz, .ok
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cp 0x01 ; if a is null, carries and unsets z
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ret c
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inc hl
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jr rdWS
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.ok:
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cp a ; ensure Z
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ret
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; Copy string from (HL) in (DE), that is, copy bytes until a null char is
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; encountered. The null char is also copied.
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; HL and DE point to the char right after the null char.
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strcpyM:
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ld a, (hl)
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ld (de), a
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inc hl
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inc de
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or a
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jr nz, strcpyM
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ret
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; Like strcpyM, but preserve HL and DE
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strcpy:
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push hl
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push de
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call strcpyM
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pop de
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pop hl
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ret
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; Compares strings pointed to by HL and DE until one of them hits its null char.
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; If equal, Z is set. If not equal, Z is reset.
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strcmp:
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push hl
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push de
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.loop:
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ld a, (de)
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cp (hl)
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jr nz, .end ; not equal? break early. NZ is carried out
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; to the caller
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or a ; If our chars are null, stop the cmp
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inc hl
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inc de
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jr nz, .loop ; Z is carried through
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.end:
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pop de
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pop hl
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; Because we don't call anything else than CP that modify the Z flag,
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; our Z value will be that of the last cp (reset if we broke the loop
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; early, set otherwise)
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ret
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; Given a string at (HL), move HL until it points to the end of that string.
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strskip:
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push bc
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ex af, af'
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xor a ; look for null char
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ld b, a
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ld c, a
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cpir ; advances HL regardless of comparison, so goes one too far
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dec hl
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ex af, af'
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pop bc
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ret
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; Returns length of string at (HL) in A.
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; Doesn't include null termination.
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strlen:
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push bc
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xor a ; look for null char
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ld b, a
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ld c, a
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cpir ; advances HL to the char after the null
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.found:
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; How many char do we have? We have strlen=(NEG BC)-1, since BC started
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; at 0 and decreased at each CPIR loop. In this routine,
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; we stay in the 8-bit realm, so C only.
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add hl, bc
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sub c
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dec a
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pop bc
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ret
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